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    SubjectRe: [PATCH 0/20] return f_fsid for statfs(2)
    On Jan 19, 2009  20:39 -0600, Dave Kleikamp wrote:
    > On Tue, 2009-01-20 at 07:36 +0800, Andreas Dilger wrote:
    > > The whole point of fsid (for NFS) is that this identifies the filesystem
    > > over reboot, even if the block device ID changes, or if the filesystem
    > > doesn't have a block device at all (e.g. cluster filesystem).
    >
    > I guess that just demonstrates how little I know about what the fsid is
    > about. Would it be preferable for file systems that have a uuid to use
    > that instead? Of course anything is an improvement over zeroes.

    Yes, that is what the ext* patches do - fold the 128-bit UUID into a 64-bit
    fsid so that it is constant across reboots. The chance of UUID collision
    is about 1/2^32 due to birthday paradox, which is fairly low, and in case
    this happens one of the filesystem UUIDs can be regenerated.

    Cheers, Andreas
    --
    Andreas Dilger
    Sr. Staff Engineer, Lustre Group
    Sun Microsystems of Canada, Inc.



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